U.S. patent application number 12/454000 was filed with the patent office on 2009-09-17 for solid-state image pickup device and method of manufacturing the same.
This patent application is currently assigned to TOPPAN PRINTING CO., LTD.. Invention is credited to Katsumi Yamamoto.
Application Number | 20090230492 12/454000 |
Document ID | / |
Family ID | 39467754 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090230492 |
Kind Code |
A1 |
Yamamoto; Katsumi |
September 17, 2009 |
Solid-state image pickup device and method of manufacturing the
same
Abstract
A solid-state image pickup device which includes a substrate
carrying a plurality of photoelectric conversion elements which are
two-dimensionally arranged therein the substrate having a plurality
of rectangular light-receiving faces each corresponding to the
photoelectric conversion element, a flattening layer having a
plurality of approximately rectangular concave faces each located
to correspond to the light-receiving faces, and a color filter
having color layers of plural kinds of colors and buried in the
concave faces of the flattening layer, the color filter exhibiting
a larger refractive index than that of the flattening layer,
wherein the color layers are respectively enabled to function as a
convex lens.
Inventors: |
Yamamoto; Katsumi; (Tokyo,
JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
TOPPAN PRINTING CO., LTD.
Tokyo
JP
|
Family ID: |
39467754 |
Appl. No.: |
12/454000 |
Filed: |
May 28, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2007/072643 |
Nov 22, 2007 |
|
|
|
12454000 |
|
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Current U.S.
Class: |
257/432 ;
257/E21.215; 257/E31.127; 438/70 |
Current CPC
Class: |
H01L 27/14603 20130101;
H01L 31/02162 20130101; H01L 31/02325 20130101; H01L 27/14627
20130101; H01L 27/14621 20130101 |
Class at
Publication: |
257/432 ; 438/70;
257/E31.127; 257/E21.215 |
International
Class: |
H01L 31/0232 20060101
H01L031/0232; H01L 31/18 20060101 H01L031/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2006 |
JP |
2006-320370 |
Claims
1. A solid-state image pickup device which comprises: a substrate
including a plurality of photoelectric conversion elements which
are two-dimensionally arranged therein, said substrate having a
plurality of rectangular light-receiving faces each corresponding
to the photoelectric conversion element; a flattening layer having
a plurality of approximately rectangular concave faces each located
to correspond to the light-receiving faces; and a color filter
including color layers of plural kinds of colors and buried in the
concave faces of the flattening layer, said color filter exhibiting
a larger refractive index than that of the flattening layer,
wherein the color layers are respectively enabled to function as a
convex lens.
2. The solid-state image pickup device according to claim 1,
wherein the flattening layer is formed of silicon dioxide or
acrylic resin.
3. The solid-state image pickup device according to claim 1,
wherein the color layers are formed of a material having a
refractive index of 1.6-1.8.
4. The solid-state image pickup device according to claim 1,
wherein said plurality of concave faces are formed directly
neighboring each other and the color layers of plural kinds of
colors are formed directly neighboring each other at the surface
thereof.
5. A method of manufacturing a solid-state image pickup device, the
method comprising: forming a transparent film on a surface of a
substrate including a plurality of photoelectric conversion
elements which are two-dimensionally arranged therein, said
substrate having a plurality of rectangular light-receiving faces
each corresponding to the photoelectric conversion element; forming
a resist pattern having bobbin-shaped or deformed bobbin-shaped
openings each being located in conformity with each of the
light-receiving faces; etching the transparent film using the
resist pattern as a mask to form a flattening layer having a
plurality of approximately rectangular concave faces each located
to correspond to the light-receiving faces; and forming a color
filter including color layers of plural kinds of colors in the
approximately rectangular concave faces and exhibiting a larger
refractive index than that of the flattening layer; wherein the
color layers are respectively enabled to function as a convex
lens.
6. The method according to claim 5, wherein the flattening layer is
formed of silicon dioxide or acrylic resin.
7. The method according to claim 5, wherein the color layers are
formed of a material having a refractive index of 1.6-1.8.
8. The method according to claim 5, wherein said plurality of
concave faces are formed directly neighboring each other and the
color layers of plural kinds of colors are formed directly
neighboring each other at the surface thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation Application of PCT Application No.
PCT/JP2007/072643, filed Nov. 22, 2007, which was published under
PCT Article 21(2) in Japanese.
[0002] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2006-320370,
filed Nov. 28, 2006, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to a solid-state image pickup device
and to a method for manufacturing the same. In particular, this
invention relates to a solid-state image pickup device wherein a
color filter is utilized also as a lens member and to a method of
manufacturing the same.
[0005] 2. Description of the Related Art
[0006] In recent years, digital cameras and video cameras utilizing
a solid-state image pickup element such as a charge coupled device
(CCD) and complementary metal oxide semiconductor (C-MOS) device
have been increasingly popularized and, at the same time, the
techniques to further miniaturize the solid-state image pickup
element by making use of a chip-size package (CSP) system have been
developed. The solid-state image pickup element of such a small
size is suitable for building into electronic equipment such as
mobile telephones where miniaturization, lightness and slimness are
desired.
[0007] Since the light-receiving face of each of the pixels of
solid-state image pickup element is constituted by a rugged
surface, it is generally practiced to deposit a transparent
flattening layer on the surface of the solid-state image pickup
element, thereby flattening the surface of the solid-state image
pickup element. More specifically, as shown in FIG. 1, a first
flattening layer 13 is deposited at first on the surface of a
solid-state image pickup element 11 in which a plurality of
photoelectric conversion elements 12 such as CCD are
two-dimensionally arranged. Then, a color filter 14 comprising
color layers of plural kinds of colors is formed on the first
flattening layer 13 and a second flattening layer 15 is formed on
the surface of the color filter 14. Furthermore, convex lenses 16
for condensing light are formed on the second flattening layer 14
(see for example, JP-A 2006-41467).
[0008] In the manufacture of the solid-state image pickup element
constructed in this manner, the first flattening layer 13, color
filter 14, second flattening layer 15 and convex lenses 16 are
required to be successively formed, raising many problems such as
the requirement of a large number of steps, deterioration of yield
and increase of manufacturing costs.
[0009] There is another problem that since a large number of
intervening layers such as the first flattening layer 13, color
filter 14 and second flattening layer 15 are interposed between the
light-receiving face and convex lens 16 and hence the
light-receiving face is fairly spaced away from the convex lens 16,
the light-collecting efficiency is degraded and attenuation of
light is more likely to occur in the path by which the light
reaches the photoelectric conversion element 12.
BRIEF SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a
solid-state image pickup device which is excellent in sensitivity
and is capable of achieving excellent color characteristics.
[0011] It is another object of the present invention to provide a
method of manufacturing a solid-state image pickup device, which
makes it possible to reduce the number of manufacturing steps, to
enhance the yield and to reduce the manufacturing costs.
[0012] According to a first aspect of the present invention, there
is provided a solid-state image pickup device which comprises: a
substrate including a plurality of photoelectric conversion
elements which are two-dimensionally arranged therein the substrate
having a plurality of rectangular light-receiving faces each
corresponding to the photoelectric conversion element; a flattening
layer having a plurality of approximately rectangular concave faces
each located to correspond to the light-receiving faces; and a
color filter including color layers of plural kinds of colors and
buried in the concave faces of the flattening layer, the color
filter exhibiting a larger refractive index than that of the
flattening layer; wherein the color layers are respectively enabled
to function as a convex lens.
[0013] According to a second aspect of the present invention, there
is provided a method of manufacturing a solid-state image pickup
device, the method comprising: forming a transparent film on a
surface of a substrate including a plurality of photoelectric
conversion elements which are two-dimensionally arranged therein,
the substrate having a plurality of rectangular light-receiving
faces each corresponding to the photoelectric conversion element;
forming a resist pattern having bobbin-shaped or deformed
bobbin-shaped openings each being located in conformity with each
of the light-receiving faces; etching the transparent film with the
resist pattern being employed as a mask to form a flattening layer
having a plurality of approximately rectangular concave faces each
located to correspond to the light-receiving faces; forming a color
filter including color layers of plural kinds of colors in the
approximately rectangular concave faces and exhibiting a larger
refractive index than that of the flattening layer; wherein the
color layers are respectively enabled to function as a convex
lens.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0014] FIG. 1 is a cross-sectional view illustrating a solid-state
image pickup device according to the prior art;
[0015] FIG. 2 is a cross-sectional view illustrating a solid-state
image pickup device according to one embodiment of the present
invention;
[0016] FIG. 3A is a plan view illustrating the configuration of the
opening of the resist pattern employed in the manufacture of the
solid-state image pickup element shown in FIG. 2;
[0017] FIG. 3B is a plan view illustrating the configuration of the
opening of the resist pattern employed in the manufacture of the
solid-state image pickup element shown in FIG. 2;
[0018] FIG. 3C is a plan view illustrating the configuration of the
opening of the resist pattern employed in the manufacture of the
solid-state image pickup element shown in FIG. 2;
[0019] FIG. 3D is a plan view illustrating the configuration of the
opening of the resist pattern employed in the manufacture of the
solid-state image pickup element shown in FIG. 2;
[0020] FIG. 4 is a diagram showing curves illustrating the process
of dry etching; and
[0021] FIG. 5 is a cross-sectional view illustrating the planar
configuration of the flattening layer that has been obtained from
dry etching.
DETAILED DESCRIPTION OF THE INVENTION
[0022] There will now be described embodiments of the present
invention.
[0023] FIG. 2 is a cross-sectional view illustrating a solid-state
image pickup device according to one embodiment of the present
invention. Referring to FIG. 2, a plurality of photoelectric
conversion elements 2 each representing a CCD, CMOS sensor, etc.,
are two-dimensionally arranged in the vicinity of the surface of a
semiconductor substrate 1. The surface portions of the
semiconductor substrate 1 which correspond to the photoelectric
conversion elements 2 represent respectively a rectangular concave
light-receiving face. A flattening layer 3 is formed to cover these
light-receiving faces. This flattening layer 3 is formed of a
transparent material such as silicon dioxide or acrylic resin for
instance.
[0024] The flattening layer 3 is provided, on the surface thereof,
with a plurality of approximately rectangular (in planar
configuration) concave faces each located to correspond to the
light-receiving faces. This flattening layer 3 having such
approximately rectangular concave faces can be formed as explained
below.
[0025] First of all, a film made of a transparent material is
formed on the surface of the semiconductor substrate 1. When this
transparent material is silicon dioxide, the film can be formed by
means of CVD or vapor deposition. When this transparent material is
acrylic resin, the film can be formed by way of the coating method.
Then, a resist pattern is formed on this transparent film. This
resist pattern is provided with bobbin-shaped or deformed
bobbin-shaped openings. Various shapes of each of such openings 10
are illustrated in FIGS. 3A-3D. The rectangular region surrounding
the opening 10 represents a light-receiving face. In FIG. 3A, a
bobbin-shaped opening 10 is shown. In FIGS. 3B-3D, the openings 10
having various deformed configurations are shown. Specifically, the
opening 10 shown in FIG. 3B has the shape in which an acute-angled
horn-like space is extended in four directions from a circular
opening. The opening 10 shown in FIG. 3C has the same shape as that
shown in FIG. 3B except that an obtuse-angled space portion is
extended from the upper and lower portions and the right and left
portions of the circular opening. The opening 10 shown in FIG. 3D
differs from the opening shown in FIG. 3C in that the upper and
lower portions and the right and left portions of the opening are
dented.
[0026] Then, by making use of this resist pattern as a mask, the
transparent film formed on the surface of the semiconductor
substrate 1 is subjected to dry etching. When the transparent film
of silicon dioxide is to be etched, a positive novolac resin
photoresist, for example, may be used as a resist and CF.sub.4 or
C.sub.2F.sub.6 may be used as an etching gas. Further, when the
transparent film of acrylic resin is to be etched, a positive
novolac resin photoresist may be used likewise as a resist and
O.sub.2+Ar, for example, may be used as an etching gas.
[0027] As for the dry etching, it is possible to employ, for
example, ECR, parallel plate magnetron, DRM, ICP or
double-frequency-type RIE.
[0028] FIG. 4 shows curves illustrating the progressing state of
dry etching. It will be recognized from FIG. 4 that, at first, the
film is etched in conformity with the configuration of the opening
of mask, thus permitting the etching to proceed not only in the
vertical direction but also in the lateral direction. Therefore,
the etching is enabled to spread to a portion of the transparent
film which is covered by the resist pattern. As a result, it is
possible to form the flattening layer 3 wherein a plurality of
approximately rectangular concave faces are directly neighboring
each other as shown in FIG. 5.
[0029] Subsequently, a resin containing a pigment dispersed therein
is coated on the flattening layer 3 and then subjected to
patterning by means of lithography. These steps are repeated for
each color, thereby creating a color filter 4 comprising
three-color layers of red (R), green (G) and blue (B) colors for
instance and filling the concave faces formed on the surface of
flattening layer 3 with these color layers.
[0030] In this case, in view of enhancing the utilization
efficiency of light, the surface of each of color layers may
preferably be configured such that these color layers are directly
neighboring without any flattening layer 3 being interposed
therebetween. Further, the surface of the color filter 4 may
preferably be flat.
[0031] As for the method to create a flat surface of the color
filter 4, it is possible to employ a method wherein each of color
filters 4 is formed by means of photolithography at first, and then
the resultant surface is polished by means of the micro-polishing
method.
[0032] The refractive index of the coloring material constituting
the color filter 4 may be higher than the refractive index of the
material constituting the flattening layer 3. For example, in a
case where the material constituting the flattening layer 3 is
acrylic resin, the refractive index of the flattening layer 3 is
1.5. Whereas, the refractive index of the coloring material
constituting the color filter 4 may be 1.6-1.8 if the coloring
material is acrylic resin containing pigments dispersed
therein.
[0033] As described above, according to this embodiment, it is
possible to form the flattening layer 3 having surface features
wherein a plurality of approximately rectangular concave faces are
directly neighboring each other by dry etching a transparent film
using a resist pattern having bobbin-shaped or deformed
bobbin-shaped openings as a mask. Further, by filling these concave
faces with color layers consisting of three kinds of
pigment-dispersed resins (i.e., red [R], green [G] and blue [B]
color layers) in a manner to make flat the surface of color layers,
it is possible to obtain a solid-state image pickup element which
is provided with the color filter 4 functioning also as a lens.
[0034] In the case of the solid-state image pickup device
constructed in this manner, since the color filter and the lens are
no longer required to be separately formed with a flattening layer
being interposed therebetween, the number of manufacturing steps
can be reduced and, at the same time, it is possible to enhance the
yield and reduce the manufacturing costs.
[0035] Further, since the convex lens (color filter 4) is disposed
close to the light-receiving face, the light-converging property
can be enhanced to realize high sensitivity. Further, since the
number of intervening layers can be minimized, it is possible to
minimize the attenuation of incident light, thus making it possible
to obtain excellent color characteristics.
[0036] According to the first aspect of the present invention,
since the approximately rectangular concave faces formed on the
surface of flattening layer are filled with color filter including
plural kinds of color layers and functioning also as a convex lens,
it is possible to dispose the convex lens (color filter) close to
light-receiving face, thereby enhancing the light-converging
property and achieving high sensitivity. Further, since the number
of intervening layers can be minimized, it is possible to provide a
solid-state image pickup device having excellent color
characteristics.
[0037] According to the second aspect of the present invention, a
flattening layer having surface features wherein a plurality of
approximately rectangular concave faces directly neighboring each
other can be formed by dry etching a transparent film using a
resist pattern having bobbin-shaped or deformed bobbin-shaped
openings as a mask, and then these concave faces are filled with
color layers formed of pigment-dispersed resin, thereby making it
possible to create color filters functioning also as a lens.
Therefore, it is possible to reduce the number of manufacturing
steps and to enhance the yield and reduce the manufacturing
costs.
* * * * *